He spent countless hours tracking down and identifying several nazis that attacked people using online footage.

No one deputized him, no one gave him a badge, he just did it because it had to be done. The designated investigative authority (cops) didn't lift a finger. And the trying authority (courts) actually gave them lenient sentences and didn't even take into account that they were white nationalists at a white nationalist march, wearing Hitler paraphernalia, engaging in hate crimes by beating the shit out of a black person for being a black person. The courts just tried them for regular assault and gave them pitiful sentences. The authority stood in the way of justice every step of the way because the perpetrators were white males, like authority always does. Authority was never about justice.

Authority enshrines itself as sacred so that anyone that would dare oppose it is in violation of the authority's laws by default. Any opposition to the authority is automatically grounds for arrest, imprisonment or execution. Rulers use the concept of authority to shield themselves from responsibility when their enforcers bomb school buses full of children or shoot black people in the face for 'resisting' their authority. Authority does not prevent polluters from doing harm, it enables them to do more harm on a much wider scale, and prevents them from having to answer for it. Authority is institutional harm with the absence of repercussions.

An individual taking it upon themselves to kill someone who is deliberately destroying an ecosystem and making countless beings sick is not the same as a state building a protected institution that can murder and pollute and not have to answer to any of its victims.

An individual deciding to take direct isolated action to stop a horrific crime against nature does not make them an authority. They have not been enshrined or officiated or certified as an authority. Their use of force is not institutional. It is an isolated action against an oppressive authority to end their violent hierarchy. Destroying a hierarchy doesn't automatically create a new hierarchy or make the person who destroyed it an authority.

Direct action taken by an anarchist against a violent authority does not somehow make the anarchist take the authority's place on the hierarchy. The anarchist doesn't start receiving the authority's paychecks or privilege or license or badge or social status. The anarchist's station in life is unchanged at best, or at worst the anarchist is imprisoned or killed for their action.

Follow up question:

Idk. Nothing you said here really had anything to do with my questions.

If it’s ok for you or other good guys to “kill them” then you’re acting as an authority.

This non-state stuff mostly seems like a way to dupe people into an ethic of isolation, the strongest survives, etc.

Answer:

Force isn't authority:

Authority is not simply an isolated instance of the use of force, but an ongoing social relationship between two parties. It is a relationship where one party has the socially legitimized right to command, and the other party has the corresponding obligation to obey.

Anarchy doesn't need to wait for states to go away. States aren't going anywhere.

(The practice) of anarchy is the opposition to authority, not the absence of it. Authority is what is allowing the earth to be polluted. Look around you. We're in the middle of a mass extinction. Authority is doing that. Not anarchy.

Archy already gives us an ethic of isolation. We're more emotionally isolated from each other than we've ever been at any point in human history.

Archy already gives us a world where only the strongest (wealthiest) survive. Where the poor are left to die on the streets or denied basic life-saving care by paramedics. Anarchy is the rejection of conditions that create these power vacuums. If you oppose authority outright, refuse to accept any authority as legitimate, you can remove yourself from culpability for the system that rubber-stamps authority so it can enslave, pollute and murder and destroy entire ecosystems.